This invention relates to pharmaceutically useful compounds, in particular compounds which are useful in the inhibition of cyclic guanosine 3xe2x80x2,5xe2x80x2-monophosphate phosphodiesterases (cGMP PDEs), such as type 5 cyclic guanosine 3xe2x80x2,5xe2x80x2-monophosphate phosphodiesterases (cGMP PDE5). The compounds therefore have utility in a variety of therapeutic areas, including male erectile dysfunction (MED).
Certain purinone derivatives for use in inhibition of cGMP PDEs are disclosed in European patent applications EP 722943, EP 722944, EP 293063 and EP 352960, international patent applications WO 96/16657 and WO 94/00453, German patent application DE 19702785 and Japanese patent application JP 63196585. Further, EP 675124 discloses purine derivatives for use as anti-inflammatory agents.
According to a first aspect of the invention there is provided compounds of formulae IA and IB, 
wherein
X represents CH or N;
R1 represents H, xe2x80x94CN, xe2x80x94C(O)N(R4)R5, xe2x80x94C(O)R4, xe2x80x94C(O)OR4, xe2x80x94N(R4)R6, xe2x80x94OR7, aryl, Het2 or lower alkyl (which alkyl group is optionally interrupted by one or more of xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94 or xe2x80x94N(R4)xe2x80x94 and/or substituted and/or terminated by one or more substituents selected from halo, xe2x80x94CN, xe2x80x94NO2, lower alkyl, xe2x80x94C(O)N(R4)R5, xe2x80x94C(O)R4, xe2x80x94C(O)OR4, xe2x80x94N(R4)R6, xe2x80x94OR7, xe2x80x94S(O)nR4, xe2x80x94S(O)nN(R4)R5, aryl and Het2);
R6 represents R5, xe2x80x94S(O)2R8, xe2x80x94S(O)2N(R4)R5, xe2x80x94C(O)R4, xe2x80x94C(O)OR8 or xe2x80x94C(O)N(R4)R5;
R7 represents R4 or xe2x80x94C(O)R4;
R3, R4, R5 and R8 independently represent, at each occurrence when used herein, lower alkyl, which alkyl group is optionally substituted and/or terminated by one or more substituents selected from lower alkyl, aryl, Het3, halo, xe2x80x94CN, xe2x80x94NO2, xe2x80x94OR9a, xe2x80x94C(O)R9b, xe2x80x94C(O)OR9c, xe2x80x94C(O)N(R9d)R9e, xe2x80x94S(O)2R10a, xe2x80x94S(O)2N(R9f)R9g, xe2x80x94OC(O)R9h and xe2x80x94N(R11)R9i;
R3, R4 and R5 may also, at each occurrence when used herein, independently represent H;
R4, R5 and R8 may also, at each occurrence when used herein, independently represent aryl;
R2 represents H, aryl, Het4 or lower alkyl, which latter group is optionally substituted and/or terminated by one or more substituents selected from lower alkyl (which latter group is optionally substituted and/or terminated by one or more substituents selected from xe2x80x94OH and halo), aryl, Het5, halo, xe2x80x94CN, xe2x80x94NO2, OR9a, xe2x80x94C(O)R9b, xe2x80x94C(O)OR9c, xe2x80x94C(O)N(R9d)R9e, xe2x80x94S(O)2R 10a, xe2x80x94S(O)2N(R9f)R9g, xe2x80x94OC(O)R9h or xe2x80x94N(R11)R9i;
R11 represents, at each occurrence when used herein, H, aryl, lower alkyl (which alkyl group is optionally substituted by one or more substituents selected from aryl and halo), xe2x80x94C(O)R9j, xe2x80x94C(O)N(R9k)R9m or xe2x80x94S(O)2R10b;
R9a to R9m independently represent, at each occurrence when used herein, H, aryl or lower alkyl (which alkyl group is optionally substituted by one or more substituents selected from aryl and halo);
R10a and R10b represent, at each occurrence when used herein, aryl or lower alkyl (which alkyl group is optionally substituted by one or more substituents selected from aryl and halo);
Het1 represents an optionally substituted four- to twelve-membered heterocyclic group, which group contains at least one nitrogen atom (via which atom the Het1 group is attached to the rest of the molecule) and, optionally, one or more further heteroatoms selected from nitrogen, oxygen and/or sulfur;
Het2 to Het5 independently represent optionally substituted four- to twelve-membered heterocyclic groups, which groups contain one or more heteroatoms selected from nitrogen, oxygen and/or sulfur;
each aryl group is optionally substituted with one or more substituents selected from halo, lower alkyl (which latter group is optionally substituted by one or more substituents selected from xe2x80x94CN, xe2x80x94NO2, xe2x80x94OR9a, xe2x80x94C(O)R9b, xe2x80x94C(O)OR9c, xe2x80x94C(O)N(R9d)R9e, xe2x80x94S(O)2N(R9f)R9g, xe2x80x94S(O)nR10a, xe2x80x94OC(O)R9h and xe2x80x94N(R11)R9i), xe2x80x94CN, xe2x80x94NO2, xe2x80x94OR9a, xe2x80x94C(O)R9b, xe2x80x94C(O)OR9c, xe2x80x94C(O)N(R9d)R9e, xe2x80x94S(O)nR10a, xe2x80x94S(O)2N(R9f)R9g, xe2x80x94OC(O)R9h and xe2x80x94N(R11)R9i;
Het1, Het2, Het3, Het4 and Het5 are each optionally substituted with one or more substituents selected from lower alkyl (which alkyl group may itself be optionally substituted and/or terminated by one or more substituents selected from lower alkyl, aryl, Het2, halo, xe2x80x94CN, xe2x80x94NO2, xe2x80x94OR9a, xe2x80x94C(O)R9b, xe2x80x94C(O)OR9c, xe2x80x94C(O)N(R9d)R9e, xe2x80x94S(O)nR10a, xe2x80x94S(O)2N(R9f)R9g, xe2x80x94OC(O)R9h and xe2x80x94N(R11)R9i), aryl, Het2, halo, xe2x80x94CN, xe2x80x94NO2, xe2x80x94OR9a, xe2x80x94C(O)R9b, xe2x80x94C(O)OR9c, xe2x80x94C(O)N(R9d)R9e, xe2x80x94S(O)nR10a, xe2x80x94S(O)2N(R9f)R9g, xe2x80x94OC(O)R9h and xe2x80x94N(R11)R9i; and
n represents, at each occurrence when used herein, 0, 1 or 2;
or a pharmaceutically, or a veterinarily, acceptable derivative thereof;
provided that when the compound is a compound of formula IB in which:
X represents CH;
R1 represents H;
R3 represents C1-8 alkyl; and
Het1 represents a 5- or 6-membered saturated heterocyclic ring, which ring is optionally substituted (via a free ring N-atom) by C1-6 alkyl (which latter group is optionally substituted by xe2x80x94OH);
then R2 does not represent:
(a) C3-11 alkyl, which C3-11 alkyl group is substituted by one of the following:
(i) in the C-1 position (relative to the purinone N-atom), by xe2x80x94C(O)R9b (wherein R9b represents H or C1-4 alkyl) or C1-11 alkyl;
(ii) in the C-2 position (relative to the purinone N-atom) by one group selected from xe2x80x94OR9a (wherein R9a represents H, C1-6 alkyl or benzyl), xe2x80x94OC(O)R9h (wherein R9h represents H, C1-6 alkyl or phenyl) and xe2x80x94N(R11)R9i (wherein R9i represents H or C1-6 alkyl and R11 represents H, C1-6 alkyl, xe2x80x94C(O)R9j (in which R9j represents H, C1-6 alkyl or phenyl) or xe2x80x94S(O)2R10b (in which R10b represents C1-4 alkyl or phenyl)) and (optionally), at the same C-2 position, by a further C1-4 alkyl group;
xe2x80x83and which C3-11 alkyl group is optionally substituted:
(I) in the C-2 to C-11 positions (relative to the purinone N-atom), by phenyl (optionally substituted by halo, xe2x80x94CN, xe2x80x94NO2, C1-6 alkyl or xe2x80x94S(O)2N(R9f)R9g, in which latter group R9f and R9g independently represent H, phenyl or lower alkyl); and/or
(II) in the C-1 position (relative to the purinone N-atom), by C1-3 alkyl;
C3-9 alkyl substituted in the C-2 to C-9 positions (relative to the purinone N-atom) by xe2x80x94N(R11)R9i (wherein R11 and R9i each independently represent H or C1-5 alkyl optionally substituted by phenyl, which latter group is substituted by xe2x80x94S(O)2N(R9f)R9g (in which R9f and R9g independently represent H, phenyl or lower alkyl)) and optionally substituted in the C-1 position (relative to the purinone N-atom) by:
(i) C1-5 alkyl (which alkyl group is optionally substituted by xe2x80x94OH); and/or
(ii) C1-3 alkyl; or
(c) C1-4 alkyl or C10-16 n-alkyl;
wherein, in the above proviso, unless otherwise indicated, alkyl, phenyl and benzyl groups are unsubstituted,
which compounds are referred to together hereinafter as xe2x80x9cthe compounds of the inventionxe2x80x9d.
The term xe2x80x9carylxe2x80x9d,when used herein, includes six- to ten-membered carbocyclic aromatic groups, such as phenyl and naphthyl. Unless otherwise specified, each aryl group identified herein is optionally substituted with one or more substituents selected from halo, lower alkyl (which latter group is optionally substituted by one or more substituents selected from xe2x80x94CN, xe2x80x94NO2, xe2x80x94OR9a, xe2x80x94C(O)R9b, xe2x80x94C(O)OR9c, xe2x80x94C(O)N(R9d)R9e, xe2x80x94S(O)2N(R9f)R9g, xe2x80x94S(O)nR10a, xe2x80x94OC(O)R9h and xe2x80x94N(R11)R9i), xe2x80x94CN, xe2x80x94NO2, xe2x80x94OR9a, xe2x80x94C(O)R9b, xe2x80x94C(O)OR9c, xe2x80x94C(O)N(R9d)R9e, xe2x80x94S(O)nR10a, xe2x80x94S(O)2N(R9f)R9g, xe2x80x94OC(O)R9h, and xe2x80x94N(R11)R9i (in which n, R9a to R9i and R10a are as hereinbefore defined). When aryl is substituted by a group containing one or more further aryl substituents, then such further aryl substituents may not be substituted by groups containing aryl substituents.
Het (Het1, Het2, Het3, Het4, Het5) groups may be fully saturated, partly unsaturated, wholly aromatic, partly aromatic and/or bicyclic in character. Unless otherwise specified, each Het (Het1, Het2, Het3, Het4, Het5) group identified herein is optionally substituted with one or more substituents selected from lower alkyl (which alkyl group may itself be optionally substituted and/or terminated as defined below in respect of R12), aryl, Het2, halo, xe2x80x94CN, xe2x80x94NO2, xe2x80x94OR9a, xe2x80x94C(O)R9b, xe2x80x94C(O)OR9c, xe2x80x94C(O)N(R9d)R9e, xe2x80x94S(O)nR10a, xe2x80x94S(O)2N(R9f)R9g, xe2x80x94OC(O)R9h, or xe2x80x94N(R11)R9i (in which n, R9a to R9i, R10a, aryl and Het2 are as hereinbefore defined). Het (Het1, Het2, Het3, Het4, Het5) groups that may be mentioned include groups such as optionally substituted azetidinyl, pyrrolidinyl, imidazolyl, indolyl, oxadiazolyl, thiadiazolyl, triazolyl, tetrazolyl, oxatriazolyl, thiatriazolyl, pyridazinyl, morpholinyl, pyrimidinyl, pyrazinyl, pyridyl, quinolinyl, isoquinolinyl, piperidinyl, pyrazolyl, imidazopyridinyl and piperazinyl, e.g. 4- R12-piperazinyl, wherein R12 represents H or lower alkyl, which latter group is optionally substituted and/or terminated by one or more substituents selected from lower alkyl, aryl, Het2, halo, xe2x80x94CN, xe2x80x94NO2, xe2x80x94OR9a, xe2x80x94C(O)R9b, xe2x80x94C(O)OR9c, xe2x80x94C(O)N(R9d)R9e, xe2x80x94S(O)nR10a, xe2x80x94S(O)2N(R9f)R9g, xe2x80x94OC(O)R9h or xe2x80x94N(R11)R9i (in which n, R9a to R9i, R10a, aryl and Het2 are as hereinbefore defined). When a Het (Het1, Het2, Het3, Het4, Het5) group is substituted either directly by a further Het2 group or by a substituent containing a further Het2 group, then such further Het2 groups may not be substituted either directly by a Het2 group or by a substituent containing a further Het2 group.
The point of attachment of any Het2, Het3, Het4 and Het5 groups may be via any atom in the ring system including (where appropriate) a heteroatom. Het (Het1, Het2, Het3, Het4, Het5) groups may also be present in the N- or S-oxidised form.
The term xe2x80x9clower alkylxe2x80x9d,when used herein, includes C1-12 alkyl, such as C1-9 alkyl (e.g. C1-6 alkyl). Unless otherwise specified, alkyl groups may, when there is a sufficient number of carbon atoms, be linear or branched, be saturated or unsaturated, be cyclic, acyclic or part cyclic/acyclic, be interrupted by oxygen, and/or be substituted by one or more halo atoms.
As defined herein, the term xe2x80x9chaloxe2x80x9d includes fluoro, chloro, bromo and iodo.
For the avoidance of doubt, each R4, R5, R8, R9a to R9m, R10a, R10b, R11 and Het2 group referred to herein is independent of other R4, R5, R8, R9a to R9m, R10a, R10b, R11 and Het groups, respectively. For example, when R2 and R4 both represent alkyl substituted by xe2x80x94OR9a, the two individual xe2x80x94OR9a substituents are independent of one another, and are not necessarily identical (though this possibility is not excluded).
The pharmaceutically or veterinarily acceptable salts of the compounds of the invention which contain a basic centre are, for example, non-toxic acid addition salts formed with inorganic acids such as hydrochloric, hydrobromic, hydroiodic, sulphuric and phosphoric acid, with carboxylic acids or with organo-sulphonic acids. Examples include the HCl, HBr, Hl, sulphate or bisulphate, nitrate, phosphate or hydrogen phosphate, acetate, benzoate, succinate, saccarate, fumarate, maleate, lactate, citrate, tartrate, gluconate, camsylate, methanesulphonate, ethanesulphonate, benzenesulphonate, p-toluenesulphonate and pamoate salts. Compounds of the invention can also provide pharmaceutically or veterinarily acceptable metal salts, in particular non-toxic alkali and alkaline earth metal salts, with bases. Examples include the sodium, potassium, aluminium, calcium, magnesium, zinc and diethanolamine salts. For a review on suitable pharmaceutical salts see Berge et al, J. Pharm, Sci., 66, 1-19, 1977. Pharmaceutically acceptable derivatives also include C1-4 alkyl ammonium salts.
The pharmaceutically acceptable solvates of the compounds of the invention include the hydrates thereof.
Also included within the scope of the compound and various salts of the invention are polymorphs thereof.
A compound of the formula (I) contains one or more asymmetric carbon atoms and therefore exists in two or more stereoisomeric forms. Where a compound of the formula (I) contains an alkenyl or alkenylene group, cis (E) and trans (Z) isomerism may also occur. The present invention includes the individual stereoisomers of the compounds of the formula (I) and, where appropriate, the individual tautomeric forms thereof, together with mixtures thereof. Separation of diastereoisomers or cis and trans isomers may be achieved by conventional techniques, e.g. by fractional crystallisation, chromatography or H.P.L.C. of a stereoisomeric mixture of a compound of the formula (I) or a suitable salt or derivative thereof. An individual enantiomer of a compound of the formula (I) may also be prepared from a corresponding optically pure intermediate or by resolution, such as by H.P.L.C. of the corresponding racemate using a suitable chiral support or by fractional crystallisation of the diastereoisomeric salts formed by reaction of the corresponding racemate with a suitable optically active acid or base, as appropriate.
All stereoisomers are included within the scope of the invention.
Abbreviations are listed at the end of this specification.
According to a further aspect of the invention there is provided compounds of formulae IA and IB as hereinbefore defined (but without the proviso), provided that, in the case of compounds of formula IB (or, in a still further aspect of the invention, in the case of compounds of formulae IA and/or IB), at least one of the following applies:
(1) R1 represents xe2x80x94CN, xe2x80x94C(O)N(R4)R5, xe2x80x94C(O)R4, xe2x80x94C(O)OR4, xe2x80x94N(R4)R6, xe2x80x94OR7, aryl, Het2 or lower alkyl (which alkyl group is optionally interrupted by one or more of xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94 or xe2x80x94N(R4)xe2x80x94 and/or substituted and/or terminated by one or more substituents selected from halo, xe2x80x94CN, xe2x80x94NO2, lower alkyl, xe2x80x94C(O)N(R4)R5, xe2x80x94C(O)R4, xe2x80x94C(O)OR4, xe2x80x94N(R4)R6, xe2x80x94OR7, xe2x80x94S(O)nR4 or xe2x80x94S(O)nN(R4)R5, aryl and Het2);
(2) R2 represents H, aryl, Het4, C1-2 alkyl (which latter group is substituted by one or more substituents selected from aryl, xe2x80x94OR9a, xe2x80x94C(O)R9b, xe2x80x94OC(O)R9h and xe2x80x94N(R11)R9i) or lower alkyl, which latter group is substituted and/or terminated by:
(i) one or more substituents selected from halo, xe2x80x94CN, xe2x80x94NO2, Het5, OR9a, xe2x80x94C(O)R9b (wherein R9a and R9b represent aryl or lower alkyl (which alkyl group is substituted by one or more halo atoms)) xe2x80x94C(O)OR9c, xe2x80x94C(O)N(R9d)R9e, xe2x80x94S(O)2R10a, xe2x80x94S(O)2N(R9f)R9g and xe2x80x94N(R11)R9i (wherein R11 represents aryl or xe2x80x94C(O)N(R9k)R9m); and/or
(ii) more than one substituent selected from xe2x80x94OR9a (wherein R9a represents aryl or lower alkyl (which alkyl group is optionally substituted by one or more substituents selected from aryl and halo)), xe2x80x94C(O)R9b, xe2x80x94OC(O)R9h and xe2x80x94N(R11)R9i;
(3) R3 represents H or lower alkyl, which alkyl group is substituted and/or terminated by one or more substituents selected from aryl, Het3, halo, xe2x80x94CN, xe2x80x94NO2, xe2x80x94OR9a, xe2x80x94C(O)R9b, xe2x80x94C(O)OR9c, xe2x80x94C(O)N(R9d)R9e, xe2x80x94S(O)2R10a, xe2x80x94S(O)2N(R9f)R9g, xe2x80x94OC(O)R9h and xe2x80x94N(R11)R9i;
(4) Het1 represents:
(i) a 4- or 7- to 12-membered optionally substituted heterocyclic group as hereinbefore defined;
(ii) a 5- or 6-membered fully saturated heterocyclic group as hereinbefore defined, which group is not substituted by C1-6 alkyl optionally substituted by xe2x80x94OH; or
(iii) a 5- or 6-membered optionally substituted, partly unsaturated or aromatic, heterocyclic group as hereinbefore defined; and/or
(5) X represents N,
wherein, unless otherwise specified, substituents n, R4, R5, R6, R7, R9a to R9m, R10a, R11, Het2, Het4 and Het5 have meanings given in the first aspect of the invention provided hereinbefore.
Preferred compounds of the invention include those wherein:
R1 represents H, xe2x80x94CN, xe2x80x94C(O)N(R4)R5, xe2x80x94C(O)R4, xe2x80x94C(O)OR4, xe2x80x94N(R4)R6, xe2x80x94OR7, aryl, Het or C1-6 alkyl (which alkyl group is optionally substituted or terminated by one or more substituents selected from halo, xe2x80x94CN, xe2x80x94NO2, lower alkyl, xe2x80x94C(O)N(R4)R5, xe2x80x94C(O)R4, xe2x80x94C(O)OR4, xe2x80x94N(R4)R6, xe2x80x94OR7, xe2x80x94S(O)nR4, xe2x80x94S(O)nN(R4)R5, aryl and Het2);
R6 represents R5, xe2x80x94S(O)2R8 or xe2x80x94C(O)R4;
R7 represents R4;
n represents 0 or 2;
R3, R4, R5 and R8 independently represent lower alkyl, which alkyl group is optionally substituted and/or terminated by one or more substituents selected from aryl, Het3, halo, xe2x80x94CN, xe2x80x94NO2, xe2x80x94OR9a or xe2x80x94N(R11)R9i;
R3, R4and R5 may also independently represent H;
R4, R5 and R8 may also independently represent aryl;
R2 represents H, aryl, Het4 or lower alkyl, which latter group is optionally substituted and/or terminated by one or more substituents selected from halo, xe2x80x94CN, xe2x80x94NO2, aryl, Het5, xe2x80x94OR9a, xe2x80x94C(O)R9b, xe2x80x94C(O)OR9c, xe2x80x94C(O)N(R9d)R9e, xe2x80x94S(O)nR10a, xe2x80x94S(O)2N(R9f)R9g or xe2x80x94N(R11)R9i;
R11 represents, at each occurrence, H, C1-6 alkyl or xe2x80x94C(O)R9j;
R9a to R9j independently represent, at each occurrence, H or C1-6 alkyl;
R10a represents C1-6 alkyl;
Het1 represents an optionally substituted (as hereinbefore defined) four- to seven-membered heterocyclic group, which group contains at least one nitrogen atom (via which atom the Het1 group is attached to the rest of the molecule) and, optionally, one or more further heteroatoms selected from nitrogen and oxygen;
Het2 to Het5 independently represent optionally substituted (as hereinbefore defined) four- to ten-membered heterocyclic groups, which groups contain between one and four heteroatoms selected from nitrogen, oxygen and/or sulfur.
More preferred compounds of the invention include those wherein:
R1 represents H, xe2x80x94C(O)N(R4)R5, xe2x80x94C(O)OR4, xe2x80x94N(R4)R6, xe2x80x94OR7, optionally substituted phenyl, Het or C1-3 alkyl (which alkyl group is optionally substituted or terminated by one or more substituents selected from halo, C1-3 alkyl, xe2x80x94C(O)N(R4)R5, xe2x80x94C(O)OR4, xe2x80x94N(R4)R6, xe2x80x94OR7, optionally substituted phenyl, and Het2);
R6 represents H, C1-4 alkyl, xe2x80x94S(O)2xe2x80x94(C1-4 alkyl) or xe2x80x94C(O)xe2x80x94(C1-4 alkyl);
R7 represents H, or C1-4 alkyl;
R3, R4, R5 independently represent H or C1-6 alkyl, which alkyl group is optionally substituted and/or terminated by one or more substituents selected from phenyl, Het3, halo, xe2x80x94OR9a or xe2x80x94N(R11)R9i;
R4 and R5 may also independently represent optionally substituted phenyl;
R2 represents H, optionally substituted phenyl, Het4 or C1-6 alkyl, which latter group is optionally substituted and/or terminated by one or more substituents selected from halo, xe2x80x94CN, xe2x80x94NO2, phenyl, Het5, xe2x80x94OR9a, xe2x80x94C(O)R9b, xe2x80x94C(O)OR9c, xe2x80x94C(O)N(R9d)R9e, xe2x80x94S(O)2xe2x80x94(C1-4 alkyl), xe2x80x94S(O)2N(R9f)R9g, or xe2x80x94N(R11)R9i;
R11 represents, at each occurrence, H or C1-4 alkyl;
R9a to R9i independently represent, at each occurrence, H or C1-4 alkyl;
Het1 represents a fully saturated, optionally substituted (as hereinbefore defined) four- to six-membered heterocyclic group, which group contains at least one nitrogen atom (via which atom the Het1 group is attached to the rest of the molecule) and, optionally, one or more further nitrogen atoms;
Het2 to Het5 independently represent four- to ten-membered heterocyclic groups, which groups contain between one and four heteroatoms selected from nitrogen, oxygen and/or sulfur, and which groups are optionally substituted by one or more substituents selected from phenyl, Het2, halo, xe2x80x94CN, xe2x80x94NO2, lower alkyl (which alkyl group is optionally substituted by one or more substituents selected from halo, phenyl, xe2x80x94OR9a and xe2x80x94N(R11)R9i), xe2x80x94OR9a, xe2x80x94C(O)R9b, xe2x80x94C(O)OR9c, xe2x80x94C(O)N(R9d)R9e, xe2x80x94S(O)2N(R9f)R9g and xe2x80x94N(R11)R9i.
Still further preferred compounds of the invention include those wherein:
R1 represents H, phenyl, Het2 or C1-2 alkyl (which alkyl group is optionally substituted or terminated by one or more substituents selected from halo, C1-2 alkyl, phenyl (which phenyl group is optionally substituted by one or more substituents selected from halo, xe2x80x94CN, xe2x80x94NO2, xe2x80x94OR9a, xe2x80x94C(O)R9b, xe2x80x94C(O)OR9c, xe2x80x94C(O)N(R9d)R9e, and xe2x80x94N(R11)R9i), and Het2);
R3 represents C1-4 alkyl, which alkyl group is optionally substituted and/or terminated by one or more substituents selected from phenyl, Het3, halo, xe2x80x94OR9a or xe2x80x94N(R11)R9i;
R2 represents H, phenyl (which phenyl group is optionally substituted by one or more substituents selected from halo, xe2x80x94CN, xe2x80x94NO2, xe2x80x94OR9axe2x80x94C(O)R9b, xe2x80x94C(O)OR9c, xe2x80x94C(O)N(R9d)R9e and xe2x80x94N(R11)R9i) or C1-4 alkyl (which alkyl group is optionally substituted and/or terminated by one or more substituents selected from halo, xe2x80x94CN, xe2x80x94NO2, phenyl, Het5, xe2x80x94OR9a or xe2x80x94N(R11)R9i);
Het1 represents a fully saturated six-membered heterocyclic group, which group contains at least one nitrogen atom (via which atom the Het1 group is attached to the rest of the molecule) and, optionally, one or more further nitrogen atoms, and which group is optionally substituted by one or more substituents selected from aryl, Het2, halo, C1-4 alkyl, xe2x80x94C(O)R9b, and xe2x80x94C(O)OR9c;
Het2 represents a six-membered optionally aromatic heterocyclic group, which group contains at least one nitrogen atom and optionally one or two further heteroatoms selected from nitrogen, oxygen and/or sulfur, and which group is optionally substituted by one or more substituents selected from halo, xe2x80x94CN, C1-4 alkyl, xe2x80x94C(O)R9b,xe2x80x94C(O)OR9c and xe2x80x94N(H)R11;
R9a to R9e, R9i and R11 represent, at each occurrence, H or C1-2 alkyl.
Particularly preferred compounds of the invention include those wherein:
R1 represents H, xe2x80x94CH3, -benzyl or -pyridyl;
R2 represents H, phenyl (which phenyl group is optionally substituted by one or more substituents selected from xe2x80x94NO2 and xe2x80x94NH2) or C1-3 alkyl; R3 represents C2-4 alkyl;
Het1 represents piperazin-1-yl, optionally substituted in the 4-position by C1-2 alkyl or pyridyl.
Preferred compounds of the invention include the compounds of the Examples described hereinafter.
Thus, according to a further aspect of the invention, there is provided a compound of formula I which, irrespective of any of the foregoing definitions and/or provisos, is:
2-[5-(4-ethylpiperazin-1-ylsulfonyl)-2-n-propoxyphenyl]-9H-purin-6-one;
8-benzyl-2-[2-ethoxy-5-(4-ethylpiperazin-1-ylsulfonyl)phenyl]-9-n-propylpurin-6-one;
2-[5-(4-ethylpiperazin-1-ylsulfonyl)-2-n-propoxyphenyl]-9-(4-nitrophenyl)purin-6-one;
9-(4-aminophenyl)-2-[5-(4-ethylpiperazin-1-ylsulfonyl)-2-n-propoxyphenyl]purin-6-one;
2-[5-(4-methylpiperazin-1-ylsulfonyl)-2-n-propoxyphenyl]-8-(pyridin-3-yl)-9H-purin-6-one;
2-[2-ethoxy-5-(4-ethylpiperazin-1-ylsulfonyl)pyridin-3-yl]-8-methyl-9-n-propylpurin-6-one;
8-benzyl-2-[2-n-butoxy-5-(4-ethylpiperazin-1-ylsulfonyl)pyridin-3-yl]-9-n-propylpurin-6-one;
2-(2-n-propoxy-5-[4-{pyridin-2-yl}piperazin-1-ylsulfonyl]phenyl)-9H-purin-6-one;
2-(2-n-propoxy-5-[4-{pyridin-2-yl}piperazin-1-ylsulfonyl]phenyl)-9-n-propylpurin-6-one;
2-[5-(4-ethylpiperazin-1-ylsulfonyl)-2-n-propoxyphenyl]-7-n-propylpurin-6-one;
2-[5-(4-ethylpiperazin-1-ylsulfonyl)-2-n-propoxyphenyl]-7-(4-nitrophenyl)purin-6-one; or
7-(4-aminophenyl)-2-[5-(4-ethylpiperazin-1-ylsulfonyl)-2-n-propoxyphenyl]purin-6-one;
which compounds may also be termed xe2x80x9ccompounds of the inventionxe2x80x9d.
Especially preferred compounds of the invention include those wherein:
R1 represents H, xe2x80x94CH3, -benzyl or -pyridyl;
R2 represents H, phenyl (which phenyl group is substituted (e.g. in position 4 relative to the point of attachment to the nitrogen atom) by one or more substituents selected from xe2x80x94NO2 and xe2x80x94NH2) or propyl;
R3 represents C2-4 alkyl;
Het1 represents piperazin-1-yl, optionally substituted in the 4-position by C1-2 alkyl.
The compounds of the invention may exhibit tautomerism. All tautomeric forms of the compounds of formulae IA and IB, and mixtures thereof, are included within the scope of the invention.
The compounds of the invention may also contain one or more asymmetric carbon atoms and may therefore exhibit optical and/or diastereoisomerism. Diastereoisomers may be separated using conventional techniques e.g. by fractional crystallisation or chromatography. The various stereoisomers may be isolated by separation of a racemic or other mixture of the compounds using conventional techniques e.g. fractional crystallisation or HPLC. The desired optical isomers may be prepared by reaction of the appropriate optically active starting materials under conditions which will not cause racemisation or epimerisation. Alternatively, the desired optical isomers may be prepared by resolution, either by HPLC of the racemate using a suitable chiral support or, where appropriate, by fractional crystallisation of the diastereoisomeric salts formed by reaction of the racemate with a suitable optically active acid or base. All stereoisomers are included within the scope of the invention.
Also included within the scope of the invention are radiolabelled derivatives of compounds of formulae IA and IB which are suitable for biological studies.
According to a further aspect of the invention there is provided processes for the preparation of compounds of the invention, as illustrated below.
The following processes are illustrative of the general synthetic procedures which may be adopted in order to obtain the compounds of the invention:
1. Compounds of formulae IA and IB may be prepared by cyclisation of corresponding compounds of formulae IIA and IIB, respectively, 
xe2x80x83wherein R1, R2, R3, Het1 and X are as hereinbefore defined.
This cyclisation may be accomplished under basic, neutral or acidic conditions using known methods for pyrimidinone ring formation. Preferably, the cyclisation is performed under basic conditions using an alkali metal salt of an alcohol or amine, such as potassium tert-butoxide or potassium bis(trimethylsilyl) amide, in the presence of a suitable solvent (e.g. an alcohol), for example at elevated (e.g. reflux) temperature (or, if a sealed vessel is employed, at above reflux temperature). The skilled person will appreciate that, when an alcohol is selected as solvent, an appropriate alcohol of formula R3OH, or a sterically hindered alcohol, e.g. 3-methyl pentan-3-ol, may be used if it is intended to mitigate alkoxide exchange at either the 2-position of the pyridin-3-yl, or the phenyl, substituent.
Compounds of formulae IIA and IIB may be prepared by reaction of corresponding compounds of formulae IIIA and IIIB, respectively, 
wherein R1 and R2 are as hereinbefore defined, with a compound of formula IV, 
or a suitable carboxylic acid derivative thereof (e.g. an acid halide or anhydride), wherein R3, Het1 and X are as hereinbefore defined.
This coupling reaction may be achieved by conventional amide bond forming techniques which are well known to those skilled in the art. For example, an acid halide (e.g. chloride) derivative of a compound of formula IV may be reacted with a compound of formula IIIA or IIIB, at between xe2x88x9210xc2x0 C. and room temperature, in the presence of an appropriate base (e.g. triethylamine, pyridine or, especially, sodium hydride) and optionally in the presence of a suitable catalyst (e.g. 4-(dimethylamino)pyridine) and/or a suitable solvent (e.g. dichloromethane, THF or N,N-dimethylformamide).
A variety of other amino acid coupling methodologies may be used to couple a compound of formula IIIA or IIIB with a compound of formula IV. For example, the acid of formula IV or a suitable salt thereof (e.g. sodium salt) may be activated with an appropriate activating reagent (e.g. a carbodiimide, such as 1,3-dicyclohexylcarbodiimide or 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride; a halotrisaminophosphonium salt such as bromotripyrrolidinophosphonium hexafluorophosphate or benzotriazol-1-yloxytrispyrrolidinophosphonium hexafluorophosphate; or a suitable pyridinium salt such as 2-chloro-1-methyl pyridinium chloride), optionally in the presence of 1-hydroxybenzotriazole hydrate and/or a catalyst such as 4-(dimethylamino)pyridine. The coupling reaction may be conducted in a suitable solvent such as dichloromethane, N,N-dimethylformamide or tetrahydrofuran, in the presence of a suitable base (e.g. sodium hydride and, optionally, 4-methylmorpholine or N-ethyldiisopropylamine), at between xe2x88x9210xc2x0 C. and +60xc2x0 C. Preferably, from about 1 to 2 molecular eqs. of the activating reagent and from 1 to 3 molecular eqs. of any base present may be employed.
Alternatively, the carboxylic acid function of IV may be activated, at between room and reflux temperature, using an excess of a reagent such as 1,1xe2x80x2-carbonyldiimidazole in an appropriate solvent, e.g. ethyl acetate, dichloromethane or butan-2-one, followed by reaction of the intermediate imidazolide, at between room and reflux temperature, with a compound of formula IIIA or IIIB.
Compounds of formula IV may be prepared by standard techniques known to those skilled in the art from a corresponding halophenyl or 3-halopyridyl precursor, via hydrolysis (e.g. under basic conditions) of an intermediate alkoxycarbonyl compound, which latter compound may be obtained by reaction of the halophenyl or 3-halopyridyl compound with carbon monoxide and a lower alkyl (e.g. C1-4) alcohol in the presence of a suitable catalyst system (e.g. tetrakis(triphenylphosphine)palladium(O)).
2. Compounds of formulae IA and IB may alternatively be prepared by reaction of corresponding compounds of formulae VA and VB, respectively, 
xe2x80x83wherein L1 is a leaving group (e.g. halo) and R1, R2, R3 and X are as hereinbefore defined, with a compound of formula VI,
Het1xe2x80x94Hxe2x80x83xe2x80x83VI
xe2x80x83wherein Het1 is as hereinbefore defined, provided that the essential nitrogen atom of the heterocycle is attached to the H-atom.
This reaction is typically performed at between xe2x88x9210xc2x0 C. and room temperature in the presence of an appropriate solvent (e.g. a C1-3 alcohol, ethyl acetate or dichloromethane), an excess of the compound of formula VI and, optionally, another suitable base (e.g. triethylamine or N-ethyldiisopropylamine).
Compounds of formula VA and VB, in which X represents N, may be prepared from corresponding compounds of formulae VIIA and VIIB, respectively, 
wherein R1, R2 and R3 are as hereinbefore defined, for example using methods known to those skilled in the art for converting an amino group to an SO2L1 group, in which L1 is as hereinbefore defined. For example, compounds of formulae VA and VB in which L1 is chloro may be prepared by reacting a corresponding compound of formula VIIA or VIIB, at between about xe2x88x9225 and about 0xc2x0 C., with about a 1.5 to 2-fold excess of sodium nitrite in a mixture of concentrated hydrochloric acid and glacial acetic acid, followed by treatment, at between xe2x88x9230xc2x0 C. and room temperature, with excess liquid sulfur dioxide and a solution of about a three-fold excess of cupric chloride in aqueous acetic acid.
Compounds of formulae VIIA and VIIB may be prepared by cyclisation of corresponding compounds of formulae VIIIA and VIIIB, respectively, 
wherein R1, R2 and R3 are as hereinbefore defined. This cyclisation may be carried out using similar techniques to those described hereinbefore for is the preparation of compounds of formulae IA and IB, but it is preferably base-mediated.
Compounds of formulae VIIIA and VIIIB may be prepared by the reduction of corresponding compounds of formulae IXA and IXB, respectively, 
wherein R1, R2 and R3 are as hereinbefore defined, for example by conventional techniques, such as catalytic hydrogenation. Typically, the hydrogenation may be achieved at between 40 and 50xc2x0 C. using a Raney(copyright) nickel catalyst in a suitable solvent (e.g. ethanol) at a hydrogen pressure of between 150 kPa and 500 kPa, especially 345 kPa.
Compounds of formulae IXA and IXB may be prepared by reaction of corresponding compounds of formulae IIIA and IIIB, as hereinbefore defined, with a compound of formula X, 
or a suitable carboxylic acid derivative (e.g. an acid halide) thereof, wherein R3 is as hereinbefore defined, for example using analogous amide bond forming techniques to those previously described for the synthesis of compounds of formulae IIA and IIB.
Compounds of formulae VIIA and VIIB may alternatively be prepared by reduction of corresponding compounds of formulae XIA and XIB, respectively: 
wherein R1, R2 and R3 are as hereinbefore defined. This reduction may be performed under a variety of reaction conditions, for example by catalytic hydrogenation (e.g. using 10% Pd/C in an alcohol, such as ethanol, at 415 kPa H2 pressure and room temperature) or by transition metal catalysed reduction (e.g. at around room temperature in the presence of iron powder (e.g. 7 eq.) in acetic acid, or TiCl3 (e.g. 9 eq.) in acetic acid).
Compounds of formulae XIA and XIB may be prepared by cyclisation of corresponding compounds of formulae IXA and IXB, respectively, for example under conditions described hereinbefore for the synthesis of compounds of formulae IA and IB.
Compounds of formulae XIA and XIB in which R1 represents lower alkyl (which alkyl group is branched and unsaturated at the carbon atom that is attached to the rest of the molecule), xe2x80x94N(R4)R5, xe2x80x94CN, aryl or Het2 (which Het2 group is either aromatic, or is unsaturated at the carbon atom that is attached to the rest of the molecule) may alternatively be prepared by reaction of corresponding compounds of formulae XIVA or XIVB, respectively, 
wherein R2, R3 and L1 are as hereinbefore defined, with a compound of formula XV,
R1aMxe2x80x83xe2x80x83XV
wherein R1a represents lower alkyl (which alkyl group is branched and unsaturated at the carbon atom that is attached to the rest of the molecule), xe2x80x94N(R4)R5, xe2x80x94CN, aryl or Het2 (which Het2 group is either aromatic, or is unsaturated at the carbon atom that is attached to M), M represents H or an optionally substituted metal or boron group, which group is suitable for cross-coupling reactions (such as a trialkylstannane (e.g. tri-n-butylstannane), a dialkylborane (e.g. diethylborane), a dialkoxyborane, a dihydroxyborane, lithium, a halomagnesium, a halozinc, copper, or a halomercury), and R4 and R5 are as hereinbefore defined, for example in the presence of an appropriate catalyst system (e.g. a palladium or nickel catalyst).
The cross-coupling reaction is preferably carried out in the presence of a base (e.g. potassium carbonate, cesium fluoride or triethylamine), preferably in excess. Those skilled in the art will appreciate that the type of catalyst that is employed will depend on factors such as the nature of the M group, and the substrate that is employed etc.
Suitable coupling conditions include so-called xe2x80x9cSuzukixe2x80x9d conditions (e.g. 1.2 eq. of boronic acid, 2 eq. of K2CO3 and 0.1 eq. of Pd(PPh3)4, refluxing in an approximately 4:1 mixture of dioxane:water, or 2.5 to 3 eq. of CsF, 0.05 to 0.1 eq. of Pd2(dba)3 and 0.01 to 0.04 eq of P(o-tol)3, refluxing in DME); or so-called xe2x80x9cStillexe2x80x9d conditions (1.5 eq. of stannane, 10 eq. of LiCl, 0.15 eq. of Cul, and 0.1 eq. of Pd(PPh3)4, refluxing in dioxane, or 5 eq. of stannane, 3.6 eq. of Et3N, Pd2(dba) and P(o-tol)3, refluxing in MeCN).
In a further typical procedure, a compound of formula XV may be used, in which M is halozinc. Such a compound may be prepared by reaction of a compound R1a-halo, where halo and R2a are as hereinbefore defined, with an alkyllithium (e.g. n-butyllithium) at between xe2x88x9278xc2x0 C. and room temperature in a suitable solvent (e.g. THF), and the resultant solution is then treated with Zn(II) chloride (solution in ether). The resulting mixture is then treated with a compound of formula XIVA or XIVB in the presence of a palladium catalyst (e.g. tetrakis(triphenyl)phosphine palladium(0)) in a suitable solvent (e.g. THF). The reaction may be carried out at between room and reflux temperature.
Compounds of formulae XIVA and XIVB in which L1 represents halo may be prepared by halogenation of corresponding compounds of formulae XIA and XIB, respectively, in which R1 represents H, under conditions known to those skilled in the art. Such conditions include, for example, in the case where L1 represents bromo, reaction at between 10 and 50xc2x0 C. with bromine in the presence of a suitable solvent (e.g. water or dichloromethane).
Compounds of formulae VA and VB, in which X is N, may alternatively be prepared from corresponding compounds of formulae XVIA and XVIB, respectively, 
wherein R1, R2 and R3 are as hereinbefore defined, for example by way of known reactions that will result in conversion of a thiol to an xe2x80x94SO2L1 group. For example, for compounds of formulae VA and VB in which L1 represents halo, the reaction may be carried out at between xe2x88x9210xc2x0 C. and reflux temperature in the presence of a suitable oxidising agent (e.g. potassium nitrate), an appropriate halogenating agent (e.g. thionyl chloride) and a suitable solvent (e.g. acetonitrile).
Compounds of formulae XVIA and XVIB may be prepared by reaction of corresponding compounds of formulae XVIIA and XVIIB, respectively, 
wherein R1, R2, R3 and L1 are as hereinbefore defined (and L1 is preferably iodo), with a suitable sulfur-delivering reagent. For example, the reaction may be carried out at between room and reflux temperature in the presence of thiourea, an appropriate coupling catalyst (e.g. dichlorobis(triethylphosphine)nickel(II) in combination with a reducing agent such as sodium cyanoborohydride) and a suitable solvent (e.g. N,N-dimethylformamide), followed by hydrolysis in the presence of a base such as calcium oxide.
Compounds of formulae XVIIA and XVIIB may be prepared by cyclisation of corresponding compounds of formulae XVIIIA and XVIIIB, respectively, 
wherein R1, R2, R3 and L1 are as hereinbefore defined. This cyclisation may be carried out using similar techniques to those described hereinbefore for the preparation of compounds of formulae IA and IB, but it is preferably base-mediated.
Compounds of formulae XVIIIA and XVIIIB may be prepared by reaction of corresponding compounds of formulae IIIA and IIIB, respectively, as hereinbefore defined, with a compound of formula XIX, 
or a suitable carboxylic acid derivative (e.g. an acid halide) thereof, wherein R3 is as hereinbefore defined, for example using analogous amide bond forming techniques to those previously described for the synthesis of compounds of formulae IIA and IIB.
Compounds of formulae VA and VB, in which X is CH, may be prepared from corresponding compounds of formulae XXA and XXB, respectively, 
wherein R1, R2 and R3 are as hereinbefore defined, for example using conventional methods for the introduction of a xe2x80x94SO2L1 group into an aromatic ring system, such as reaction of a compound of formula XXA or XXB, optionally in the presence of an appropriate solvent (e.g. dichloromethane), with a compound of formula L1SO3H and (optionally) a compound of formula SO(L1)2. When L1 is chloro, reaction may take place at between 0xc2x0 C. and room temperature in the presence of an excess of chlorosulfonic acid (optionally in conjunction with an excess of thionyl chloride), and optionally in an appropriate organic solvent (e.g. dichloromethane).
Compounds of formulae XXA and XXB are available using known techniques. For example, compounds of formulae XXA and XXB, in which R2 represents aryl, Het4 or optionally substituted lower alkyl, may be prepared by reaction of corresponding compounds of formulae XXA and XXB, respectively, in which R2 represents H, with a compound of formula XXI,
R2axe2x80x94L2xe2x80x83xe2x80x83XXI
wherein R2a represents aryl, Het4 or lower alkyl (which latter group is optionally substituted as defined hereinbefore in respect of R2 in compounds of formulae IA and IB), and L2 represents a leaving group such as halo, alkane sulfonate, perfluoroalkane sulfonate or arene sulfonate, for example using methods which are known to those skilled in the art. Preferably, the leaving group is halo (preferably chloro, bromo or iodo) and the reaction is performed at between xe2x88x9270 and 140xc2x0 C. in the presence of a suitable base (e.g. cesium carbonate, potassium hydroxide or sodium hydride), an appropriate solvent (e.g. N,N-dimethylformamide, DMSO or THF), and optionally in the presence of sodium iodide or potassium iodide. Preferably the alkylation is conducted at between room temperature and 80xc2x0 C.
Those skilled in the art will appreciate that, in compounds of formula XXI in which R2a represents Het4 or aryl, the R2 group may need to be activated by the presence of one or more electron-withdrawing groups for reaction with compounds of formulae XXA and XXB (in which R2 represents H) to take place. Suitable electron-withdrawing groups for this purpose include nitro, formyl, acyl and alkoxycarbonyl. Such groups may be introduced and/or removed from the relevant aryl or Hete group using methods and under conditions that are known to those skilled in the art.
Compounds of formulae XXA and XXB in which R2 represents optionally substituted lower alkyl may be obtained by reaction of compounds of formulae XXA and XXB, respectively, in which R2 represents H, with a compound of formula XXII,
R2bxe2x80x94OHxe2x80x83xe2x80x83XXII
wherein R2b represents lower alkyl (which alkyl group is optionally substituted as defined hereinbefore in respect of R2 in compounds of formulae IA and IB), for example under Mitsunobu-type conditions known to those skilled in the art.
Compounds of formulae XXA and XXB may alternatively be prepared by cyclisation of corresponding compounds of formulae XXIIIA and XXIIIB, respectively, 
wherein R1, R2 and R3 are as hereinbefore defined, for example under analogous conditions to those described previously for the synthesis of compounds of formulae IA and IB.
Compounds of formulae XXIIIA and XXIIIB may be prepared by reaction of corresponding compounds of formulae IIIA or IIIB, respectively, as hereinbefore defined, with a compound of formula XXIV, 
or a suitable carboxylic acid derivative (e.g. an acid halide) thereof, wherein R3 is as hereinbefore defined, for example using analogous amide bond forming techniques to those previously described for the synthesis of compounds of formulae IIA and IIB.
Compounds of formulae XXIIIA and XXIIIB may alternatively be prepared by reaction of corresponding compounds of formulae XXIVA or XXIVB, respectively, 
wherein R13 represents a lower (e.g. C1-6) alkyl group and R1 and R2 are as hereinbefore defined, with a compound of formula XXIV, as hereinbefore defined, followed by conversion of the xe2x80x94C(O)OR13 group of the resultant amide into a xe2x80x94C(O)NH2 group, using conventional techniques known to those skilled in the art. In a particular embodiment, the conversion of the xe2x80x94C(O)OR13 group to a primary amide function and cyclisation of the resultant compound of formula XXIIIA or XXIIIB (to give a compound of formula XXA or XXB, respectively), may be accomplished in a one-pot procedure. Preferably, this one-pot procedure is accomplished with a saturated methanolic ammonia solution, in the presence of base (e.g. potassium t-butoxide), under pressure, at elevated temperatures, especially at 100xc2x0 C.
Compounds of formulae XXA and XXB in which R2 represents H may be prepared by reaction of a corresponding compound of formula XXV, 
wherein R3 is as hereinbefore defined, with a compound of formula XXVI,
R1xe2x80x94CHOxe2x80x83xe2x80x83XXVI
wherein R1 is as hereinbefore defined, for example at between room and reflux temperature, optionally in the presence of a suitable mild oxidant (e.g. sodium metabisulfite), and optionally in an appropriate organic solvent (e.g. N,N-dimethyl acetamide).
Compounds of formulae XXA and XXB in which R2 represents H may alternatively be prepared by reaction of a corresponding compound of formula XXV, as hereinbefore defined, with a compound of formula XXVII,
R1xe2x80x94C(O)OHxe2x80x83xe2x80x83XXVII
or a suitable carboxylic acid derivative thereof (e.g. an acid halide or an ortho ester), for example at between room and reflux temperature, optionally in the presence of a suitable solvent (e.g. N,N-dimethyl formamide) and/or an appropriate base.
3. Compounds of formulae IA and IB, in which R2 represents aryl, Het4 or optionally substituted lower alkyl, may be prepared by reaction of corresponding compounds of formulae IA and IB in which R2 represents H with a compound of formula XXI, as hereinbefore defined, for example as described hereinbefore for preparation of compounds of formulae XXA and XXB.
4. Compounds of formulae IA and IB, in which R2 represents optionally substituted lower alkyl, may be prepared by reaction of corresponding compounds of formulae IA and IB in which R2 represents H with a compound of formula XXII, as hereinbefore defined, for example as described hereinbefore for preparation of compounds of formulae XXA and XXB.
Compounds of formulae IIIA, IIIB, VI, X, XV, XIX, XXI, XXII, XXIV, XXIVA. XXIVB, XXV, XXVI, XXVII and derivatives thereof, when not commercially available or not subsequently described, may be obtained either by analogy with the processes described hereinbefore, or by conventional synthetic procedures, in accordance with standard techniques, from readily available starting materials using appropriate reagents and reaction conditions. For example, compounds of formula XXV may be prepared by, or by analogy with, methods described in EP 352 960.
Substituents on aryl and Het (Het1, Het2, Het3, Het4, Het5) groups in the above-mentioned compounds may be introduced, removed and interconverted, using techniques which are well known to those skilled in the art. For example, compounds of formulae IA and IB as described hereinbefore, in which R2 represents an aminophenyl group, may be prepared by reducing corresponding compounds of formula IA or IB, in which R2 represents a nitrophenyl group. The reaction may be performed using methods which are well known to those skilled in the art, for example under reduction conditions described hereinbefore.
The skilled person will also appreciate that various standard substituent or functional group interconversions and transformations within certain compounds of formulae IA and IB will provide other compounds of formulae IA and IB. For example, alkoxide exchange at the 2-position of the 5-phenyl and the pyridin-3-yl substituents. Moreover, certain compounds of formulae IA and IB, for example those in which Het1 represents a 4-R12-piperazinyl group, in which R12 does not represent H, may be prepared directly from the corresponding piperazine analogues in which R12 represents H, using standard procedures (e.g. alkylation).
The compounds of the invention may be isolated from their reaction mixtures using conventional techniques.
It will be appreciated by those skilled in the art that, in the course of carrying out the processes described above, the functional groups of intermediate compounds may need to be protected by protecting groups.
Functional groups which it is desirable to protect include hydroxy, amino and carboxylic acid. Suitable protecting groups for hydroxy include trialkylsilyl and diarylalkylsilyl groups (e.g. tert-butyidimethylsilyl, tert-butyidiphenylsilyl or trimethylsilyl), tetrahydropyranyl and alkylcarbonyl groups (e.g. methyl- and ethylcarbonyl). Suitable protecting groups for amino include tert-butyloxycarbonyl, 9-fluorenylmethoxycarbonyl or benzyloxycarbonyl. Suitable protecting groups for carboxylic acid include C1-6 alkyl or benzyl esters.
The protection and deprotection of functional groups may take place before or after any of the reaction steps described hereinbefore.
Protecting groups may be removed in accordance with techniques which are well known to those skilled in the art.
The use of protecting groups is fully described in xe2x80x9cProtective Groups in Organic Chemistryxe2x80x9d, edited by J W F McOmie, Plenum Press (1973), and xe2x80x9cProtective Groups in Organic Synthesisxe2x80x9d, 2nd edition, T W Greene and P G M Wutz, Wiley-Interscience (1991).
Persons skilled in the art will also appreciate that, in order to obtain compounds of formula I in an alternative, and, on some occasions, more convenient, manner, the individual process steps mentioned hereinbefore may be performed in a different order, and/or the individual reactions may be performed at a different stage in the overall route (i.e. substituents may be added to and/or chemical transformations performed upon, different intermediates to those mentioned hereinbefore in conjunction with a particular reaction). This will depend inter alia on factors such as the nature of other functional groups present in a particular substrate, the availability of key intermediates and the protecting group strategy (if any) to be adopted. Clearly, the type of chemistry involved will influence the choice of reagent that is used in the said synthetic steps, the need, and type, of protecting groups that are employed, and the sequence for accomplishing the synthesis.
Pharmaceutically acceptable acid addition salts of the compounds of formulae IA and IB which contain a basic centre may be prepared in a conventional manner. For example, a solution of the free base may be treated with the appropriate acid, either neat or in a suitable solvent, and the resulting salt may then be isolated either by filtration or by evaporation under vacuum of the reaction solvent. Pharmaceutically acceptable base addition salts can be obtained in an analogous manner by treating a solution of a compound of formula IA or IB with the appropriate base. Both types of salt may be formed or interconverted using ion-exchange resin techniques.
The present invention also includes all suitable isotopic variations of a compound of the formula (I) or a pharmaceutically acceptable salt thereof. An isotopic variation of a compound of the formula (I) or a pharmaceutically acceptable salt thereof is defined as one in which at least one atom is replaced by an atom having the same atomic number but an atomic mass different from the atomic mass usually found in nature. Examples of isotopes that can be incorporated into compounds of the formula (I) and pharmaceutically acceptable salts thereof include isotopes of hydrogen, carbon, nitrogen, oxygen, phosphorus, sulphur, fluorine and chlorine such as 2H, 3H, 13C, 14C, 15N, 17O, 18O, 31P, 32P, 35S, 18F and 36Cl , respectively. Certain isotopic variations of the compounds of the formula (I) and pharmaceutically acceptable salts thereof, for example, those in which a radioactive isotope such as 3H or 14C is incorporated, are useful in drug and/or substrate tissue distribution studies. Tritiated, i.e., 3H, and carbon-14, i.e., 14C, isotopes are particularly preferred for their ease of preparation and detectability. Further, substitution with isotopes such as deuterium, i.e., H, may afford certain therapeutic advantages resulting from greater metabolic stability, for example, increased in vivo half-life or reduced dosage requirements and hence may be preferred in some circumstances. Isotopic variations of the compounds of formula (I) and pharmaceutically acceptable salts thereof of this invention can generally be prepared by conventional procedures such as by the illustrative methods or by the preparations described in the Examples and Preparations hereafter using appropriate isotopic variations of suitable reagents.
It will be appreciated by those skilled in the art that certain protected derivatives of compounds of formulae IA or IB, which may be made prior to a final deprotection stage, may not possess pharmacological activity as such, but may, in certain instances, be administered orally or parenterally and thereafter metabolised in the body to form compounds of the invention which are pharmacologically active. Such derivatives may therefore be described as xe2x80x9cprodrugsxe2x80x9d.Further, certain compounds of formulae IA and IB may act as prodrugs of other compounds of formulae IA and IB, respectively.
All protected derivatives, and prodrugs, of compounds of formulae IA and IB are included within the scope of the invention.
The present invention additionally comprises the combination of a cGMP PDE5 inhibitor, in particular a compound of the general formula (I) with:
(a) one or more naturally occurring or synthetic prostaglandins or esters thereof. Suitable prostaglandins for use herein include compounds such as alprostadil, prostaglandin E1,prostaglandin E0, 13, 14-dihydroprosta glandin E1, prostaglandin E2, eprostinol, natural synthetic and semi-synthetic prostaglandins and derivatives thereof including those described in U.S. Pat. No. 6,037,346 issued on Mar. 14, 2000 and incorporated herein by reference, PGE0, PGE1, PGA1, PGB1, PGF1 xcex1, 19-hydroxy PGA1, 19-hydroxy-PGB1, PGE2, PGB2, 19-hydroxy-PGA2, 19-hydroxy-PGB2, PGE3xcex1, carboprost tromethamine dinoprost, tromethamine, dinoprostone, lipo prost, gemeprost, metenoprost, sulprostune, tiaprost and moxisylate; and/or
(b) one or more xcex1-adrenergic receptor antagonist compounds also known as xcex1-adrenoceptors or xcex1-receptors or xcex1-blockers. Suitable compounds for use herein include: the xcex1-adrenergic receptors as described in PCT application WO99/30697 published on Jun. 14, 1998, the disclosures of which relating to xcex1-adrenergic receptors are incorporated herein by reference and include, selective xcex11-adrenoceptors or xcex12-adrenoceptors and non-selective adrenoceptors, suitable xcex11-adrenoceptors include: phentolamine, phentolamine mesylate, trazodone, alfuzosin, indoramin, naftopidil, tamsulosin, dapiprazole, phenoxybenzamine, idazoxan, efaraxan, yohimbine, rauwolfa alkaloids, Recordati 15/2739, SNAP 1069, SNAP 5089, RS17053, SL 89.0591, doxazosin, terazosin, abanoquil and prazosin; xcex12-blockers from U.S. Pat. No. 6,037,346 Mar. 14, 2000] dibenarnine, tolazoline, trimazosin an d dibenarnine; xcex1-adrenergic receptors as described in U.S. Pat. Nos.: 4,188,390; 4,026,894; 3,511,836; 4,315,007; 3,527,761; 3,997,666; 2,503,059; 4,703,063; 3,381,009; 4,252,721 and 2,599,000 each of which is incorporated herein by reference; xcex12-Adrenoceptors include: clonidine, papaverine, papaverine hydrochloride, optionally in the presence of a cariotonic agent such as pirxamine; and/or
(c) one or more NO-donor (NO-agonist) compounds. Suitable NO-donor compounds for use herein include organic nitrates, such as mono- di or tri-nitrates or organic nitrate esters including glyceryl brinitrate (also know n a s nitroglycerin), isosorbide 5-mononitrate, isosorbide dinitrate, pentaerythritol tetranitrate, erythrityl tetranitrate, sodium nitroprusside (SNP), 3-morpholinosydnonimine molsidomine, S-nitroso- N-acetyl penicilliamine (SNAP) S-nitroso-N-glutathione (SNO-GLU), N-hydroxyxe2x80x94L-arginine, amylnitrate, linsidomine, linsidomine chlorohydrate, (SIN-1) S-nitroso-N-cysteine, diazenium diolates,(NONOates), 1,5-pentanedinitrate,L-arginene, ginseng, zizphi fructus, molsidomine, Re-2047, nitrosylated maxisylyte derivatives such as NMI-678-11 and NMI-937 as described in published PCT application WO 0012075; and/or
(d) one or more potassium channel openers. Suitable potassium channel openers for use herein include nicorandil, cromokalim, levcromakalim, lemakalim, pinacidil, cliazoxide, minoxidil, charybdotoxin, glyburide, 4-amini pyridine, BaCl2; and/or
(e) one or more dopaminergic agents. Suitable dopaminergic compounds for use herein include D2-agonists such as, pramipexol; apomorphine; and/or
(f) one or more vasodilator agents. Suitable vasodilator agents for use herein include nimodepine, pinacidil, cyclandelate, isoxsuprine, chloroprumazine, halo peridol, Rec 15/2739, trazodone, pentoxifylline; and/or
(g) one or more thromboxane A2 agonists; and/or
(h) one or more CNS active agents; and/or
(i) one or more ergot alkoloids; Suitable ergot alkaloids are described in U.S. Pat. No. 6,037,346 issued on Mar. 14, 2000 and include acetergamine, brazergoline, bromerguride, cianergoline, delorgotrile, disulergine, ergonovine maleate, ergotamine tartrate, etisulergine, lergotrile, lysergide, mesulergine, metergoline, metergotamine, nicergoline, pergolide, propisergide, proterguride, terguride; and/or
(k) one or more compounds which modulate the action of atrial natruretic factor (also known as atrial naturetic peptide), such as inhibitors or neutral endopeptidase; and/or
(l) one or more compounds which inhibit angiotensin-converting enzyme such as enapril, and combined inhibitors of angiotensin-converting enzyme and neutral endopeptidase such as omapatrilat; and/or
(m)one or more angiotensin receptor antagonists such as losartan; and/or
(n) one or more substrates for NO-synthase, such as L-arginine; and/or
(o) one or more calcium channel blockers such as amlodipine; and/or
(p) one or more antagonists of endothelin receptors and inhibitors or endothelin-converting enzyme; and/or
(q) one or more cholesterol lowering agents such as statins and fibrates; and/or
(r) one or more antiplatelet and antithrombotic agents, e.g. tPA, uPA, warfarin, hirudin and other thrombin inhibitors, heparin, thromboplastin activating factor inhibitors; and/or
(s) one or more insulin sensitising agents such as rezulin and hypoglycaemic agents such as glipizide; and/or
(t) L-DOPA or carbidopa; and/or
(u) one or more acetylcholinesterase inhibitors such as donezipil; and/or
(v) one or more steroidal or non-steroidal anti-inflammatory agents.
The compounds of the invention are useful because they possess pharmacological activity in animals, especially mammals, including humans. They are therefore indicated as pharmaceuticals, as well as for use as animal medicaments.
According to a further aspect of the invention there is provided the compounds of the invention for use as pharmaceuticals, and for use as animal medicaments.
In particular, compounds of the invention have been found to be potent and selective inhibitors of cGMP PDEs, such as cGMP PDE5, for example as demonstrated in the tests described below, and are thus useful in the treatment of medical conditions in humans, and in animals, in which cGMP PDEs, such as cGMP PDE5, are indicated, and in which inhibition of cGMP PDEs, such as cGMP PDE5, is desirable.
By the term xe2x80x9ctreatmentxe2x80x9d, we include both therapeutic (curative), palliative or prophylactic treatment.
Thus, according to a further aspect of the invention there is provided the use of the compounds of the invention in the manufacture of a medicament for the treatment of a medical condition in which a cGMP PDE (e.g. cGMP PDE5) is indicated. There is further provided the use of the compounds of the invention in the manufacture of a medicament for the treatment of a medical condition in which inhibition of a cGMP PDE (e.g. cGMP PDE5) is desirable.
The compounds of the invention are thus expected to be useful for the curative, palliative or prophylactic treatment of mammalian sexual disorders. In particular, the compounds are of value in the treatment of mammalian sexual dysfunctions such as male erectile dysfunction (MED), impotence, female sexual dysfunction (FSD), clitoral dysfunction, female hypoactive sexual desire disorder, female sexual arousal disorder, female sexual pain disorder or female sexual orgasmic dysfunction (FSOD) as well as sexual dysfunction due to spinal cord injury but, clearly, will be useful also for treating other medical conditions for which a potent and selective cGMP PDE5 inhibitor is indicated. Such conditions include premature labour, dysmenorrhoea, benign prostatic hyperplasia (BPH), bladder outlet obstruction, incontinence, stable, unstable and variant (Prinzmetal) angina, hypertension, pulmonary hypertension, chronic obstructive pulmonary disease, coronary artery disease, congestive heart failure, atherosclerosis, conditions of reduced blood vessel patency, e.g. post-percutaneous transluminal coronary angioplasty (post-PTCA), peripheral vascular disease, stroke, nitrate induced tolerance, bronchitis, allergic asthma, chronic asthma, allergic rhinitis, glaucoma and diseases characterised by disorders of gut motility, e.g. irritable bowel syndrome (IBS).
Further medical conditions for which a potent and selective cGMP PDE5 inhibitor is indicated, and for which treatment with compounds of the present invention may be useful include pre-eclampsia, Kawasaki""s syndrome, nitrate tolerance, multiple sclerosis, diabetic nephropathy, peripheral diabetic neuropathy, Alzheimer""s disease, acute respiratory failure, psoriasis, skin necrosis, cancer, metastasis, baldness, nutcracker oesophagus, anal fissure, haemorrhoids and hypoxic vasoconstriction.
Particularly preferred conditions include MED and FSD.
Thus the invention provides a method of treating or preventing a medical condition for which a cGMP PDE5 inhibitor is indicated, in an animal (e.g. a mammal, including a human being), which comprises administering a therapeutically effective amount of a compound of the invention to a mammal in need of such treatment.
The compounds of the invention will normally be administered orally or by any parenteral route, in the form of pharmaceutical preparations comprising the active ingredient, optionally in the form of a non-toxic organic, or inorganic, acid, or base, addition salt, in a pharmaceutically acceptable dosage form. Depending upon the disorder and patient to be treated, as well as the route of administration, the compositions may be administered at varying doses.
The compounds of the invention may also be combined with any other drugs useful in the inhibition of cGMP-PDEs, such as cGMP-PDE5.
The compounds of formulae (IA) or (1B), their pharmaceutically acceptable salts, and pharmaceutically acceptable solvates of either entity can be administered alone but, in human therapy will generally be administered in admixture with a suitable pharmaceutical excipient diluent or carrier selected with regard to the intended route of administration and standard pharmaceutical practice.
For example, the compounds of formulae (IA) or (1B) or salts or solvates thereof can be administered orally, buccally or sublingually in the form of tablets, capsules (including soft gel capsules), ovules, elixirs, solutions or suspensions, which may contain flavouring or colouring agents, for immediate-, delayed-, modified-, sustained-, controlled-release or pulsatile delivery applications. The compounds of the invention may also be administered via intracavernosal injection. The compounds of the invention may also be administered via fast dispersing or fast dissolving dosages forms.
Such tablets may contain excipients such as microcrystalline cellulose, lactose, sodium citrate, calcium carbonate, dibasic calcium phosphate and glycine, disintegrants such as starch (preferably corn, potato or tapioca starch), sodium starch glycollate, croscarmellose sodium and certain complex silicates, and granulation binders such as polyvinylpyrrolidone, hydroxypropylmethyl cellulose (HPMC), hydroxypropylcellulose (HPC), sucrose, gelatin and acacia. Additionally, lubricating agents such as magnesium stearate, stearic acid, glyceryl behenate and talc may be included.
Solid compositions of a similar type may also be employed as fillers in gelatin capsules. Preferred excipients in this regard include lactose, starch, a cellulose, milk sugar or high molecular weight polyethylene glycols. For aqueous suspensions and/or elixirs, the compounds of the formula (IA) or (IB) may be combined with various sweetening or flavouring agents, colouring matter or dyes, with emulsifying and/or suspending agents and with diluents such as water, ethanol, propylene glycol and glycerin, and combinations thereof.
Modified release and pulsatile release dosage forms may contain excipients such as those detailed for immediate release dosage forms together with additional excipients that act as release rate modifiers, these being coated on and/or included in the body of the device. Release rate modifiers include, but are not exclusively limited to, hydroxypropylmethyl cellulose, methyl cellulose, sodium carboxymethylcellulose, ethyl cellulose, cellulose acetate, polyethylene oxide, Xanthan gum, Carbomer, ammonio methacrylate copolymer, hydrogenated castor oil, carnauba wax, paraffin wax, cellulose acetate phthalate, hydroxypropylmethyl cellulose phthalate, methacrylic acid copolymer and mixtures thereof. Modified release and pulsatile release dosage forms may contain one or a combination of release rate modifying excipients. Release rate modifying excipients maybe present both within the dosage form i.e. within the matrix, and/or on the dosage form i.e. upon the surface or coating.
Fast dispersing or dissolving dosage formulations (FDDFs) may contain the following ingredients: aspartame, acesulfame potassium, citric acid, croscarmellose sodium, crospovidone, diascorbic acid, ethyl acrylate, ethyl cellulose, gelatin, hydroxypropylmethyl cellulose, magnesium stearate, mannitol, methyl methacrylate, mint flavouring, polyethylene glycol, fumed silica, silicon dioxide, sodium starch glycolate, sodium stearyl fumarate, sorbitol, xylitol.
The compounds of the invention can also be administered parenterally, for example, intracavernosally, intravenously, intra-arterially, intraperitoneally, intrathecally, intraventricularly, intraurethrally intrasternally, intracranially, intramuscularly or subcutaneously, or they may be administered by infusion techniques. For such parenteral administration they are best used in the form of a sterile aqueous solution which may contain other substances, for example, enough salts or glucose to make the solution isotonic with blood. The aqueous solutions should be suitably buffered (preferably to a pH of from 3 to 9), if necessary. The preparation of suitable parenteral formulations under sterile conditions is readily accomplished by standard pharmaceutical techniques well-known to those skilled in the art.
For oral and parenteral administration to human patients, the daily dosage level of the compounds of formula (IA) or (1B) or salts or solvates thereof will usually be from 10 to 500 mg (in single or divided doses).
Thus, for example, tablets or capsules of the compounds of formulae (IA) or (IB) or salts or solvates thereof may contain from 5 mg to 250 mg of active compound for administration singly or two or more at a time, as appropriate. The physician in any event will determine the actual dosage which will be most suitable for any individual patient and it will vary with the age, weight and response of the particular patient. The above dosages are exemplary of the average case. There can, of course, be individual instances where higher or lower dosage ranges are merited and such are within the scope of this invention. The skilled person will also appreciate that, in the treatment of certain conditions (including MED and FSD), compounds of the invention may be taken as a single dose on an xe2x80x9cas requiredxe2x80x9d basis (i.e. as needed or desired).
In general a tablet formulation could typically contain between about 0.1 mg and 500 mg of a compound according to the present invention (or a salt thereof whilst tablet fill weights may range from 50 mg to 1000 mg. An example formulation for a 10 mg tablet is illustrated:
The compounds of the invention can also be administered intranasally or by inhalation and are conveniently delivered in the form of a dry powder inhaler or an aerosol spray presentation from a pressurised container, pump, spray or nebuliser with the use of a suitable propellant, e.g. dichlorodifluoromethane, trichlorofluoromethane, dichlorotetrafluoroethane, a hydrofluoroalkane such as 1,1,1,2-tetrafluoroethane (HFA 134A [trade mark] or 1,1,1,2,3,3,3-heptafluoropropane (HFA 227EA [trade mark]), carbon dioxide or other suitable gas. In the case of a pressurised aerosol, the dosage unit may be determined by providing a valve to deliver a metered amount. The pressurised container, pump, spray or nebuliser may contain a solution or suspension of the active compound, e.g. using a mixture of ethanol and the propellant as the solvent, which may additionally contain a lubricant, e.g. sorbitan trioleate. Capsules and cartridges (made, for example, from gelatin) for use in an inhaler or insufflator may be formulated to contain a powder mix of a compound of the formula (IA) or (IB) and a suitable powder base such as lactose or starch.
Aerosol or dry powder formulations are preferably arranged so that each metered dose or xe2x80x9cpuffxe2x80x9d contains from 1 to 50 mg of a compound of the formula (IA) or (IB) for delivery to the patient. The overall daily dose with an aerosol will be in the range of from 1 to 50 mg which may be administered in a single dose or, more usually, in divided doses throughout the day.
The compounds of the invention may also be formulated for delivery via an atomiser. Formulations for atomiser devices may contain the following ingredients as solubilisers, emulsifiers or suspending agents: water, ethanol, glycerol, propylene glycol, low molecular weight polyethylene glycols, sodium chloride, fluorocarbons, polyethylene glycol ethers, sorbitan trioleate, oleic acid.
Alternatively, the compounds of the formulae (IA) or (IB) or salts or solvates thereof can be administered in the form of a suppository or pessary, or they may be applied topically in the form of a gel, hydrogel, lotion, solution, cream, ointment or dusting powder. The compounds of the formulae (IA) and (IB) or salts or solvates thereof may also be dermally administered. The compounds of the formulae (IA) or (IB) or salts or solvates thereof may also be transdermally administered, for example, by the use of a skin patch. They may also be administered by the ocular, pulmonary or rectal routes.
For ophthalmic use, the compounds can be formulated as micronised suspensions in isotonic, pH adjusted, sterile saline, or, preferably, as solutions in isotonic, pH adjusted, sterile saline, optionally in combination with a preservative such as a benzylalkonium chloride. Alternatively, they may be formulated in an ointment such as petrolatum.
For application topically to the skin, the compounds of the formulae (IA) or (IB) or salts or solvates thereof can be formulated as a suitable ointment containing the active compound suspended or dissolved in, for example, a mixture with one or more of the following: mineral oil, liquid petrolatum, white petrolatum, propylene glycol, polyoxyethylene polyoxypropylene compound, emulsifying wax and water. Alternatively, they can be formulated as a suitable lotion or cream, suspended or dissolved in, for example, a mixture of one or more of the following: mineral oil, sorbitan monostearate, a polyethylene glycol, liquid paraffin, polysorbate 60, cetyl esters wax, cetearyl alcohol, 2-octyldodecanol, benzyl alcohol and water.
The compounds of the formula (IA) or (IB) may also be used in combination with a cyclodextrin. Cyclodextrins are known to form inclusion and non-inclusion complexes with drug molecules. Formation of a drug-cyclodextrin complex may modify the solubility, dissolution rate, bioavailability and/or stability property of a drug molecule. Drug-cyclodextrin complexes are generally useful for most dosage forms and administration routes. As an alternative to direct complexation with the drug the cyclodextrin may be used as an auxiliary additive, e.g. as a carrier, diluent or solubiliser. Alpha-, beta- and gamma-cyclodextrins are most commonly used and suitable examples are described in WO-A-91/11172, WO-A-94/02518 and WO-A-98/55148.
Generally, in humans, oral administration of the compounds of the invention is the preferred route, being the most convenient and, for example in MED, avoiding the well-known disadvantages associated with intracavernosal (i.c.) administration. A preferred oral dosing regimen in MED for a typical man is from 25 to 250 mg of compound when required. In circumstances where the recipient suffers from a swallowing disorder or from impairment of drug absorption after oral administration, the drug may be administered parenterally, sublingually or buccally.
For veterinary use, a compound of formula (IA) or (IB), or a veterinarily acceptable salt thereof, or a veterinarily acceptable solvate or pro-drug thereof, is administered as a suitably acceptable formulation in accordance with normal veterinary practice and the veterinary surgeon will determine the dosing regimen and route of administration which will be most appropriate for a particular animal.
Thus, according to a further aspect of the invention there is provided a pharmaceutical formulation including a compound of the invention in admixture with a pharmaceutically or veterinarily acceptable adjuvant, diluent or carrier.
In addition to the fact that compounds of the invention inhibit cyclic guanosine 3xe2x80x2,5xe2x80x2-monophosphate phosphodiesterases (cGMP PDEs) and in particular, are potent and selective inhibitors of cGMP PDE5, compounds of the invention may also have the advantage that they may be more efficacious than, be less toxic than, have a broader range of activity than, be more potent than, produce fewer side effects than, be more easily absorbed than, or they may have other useful pharmacological properties over, compounds known in the prior art.
The biological activities of the compounds of the present invention were determined by the following test methods.
In vitro PDE inhibitory activities against cyclic guanosine 3xe2x80x2,5xe2x80x2-monophosphate (cGMP) and cyclic adenosine 3xe2x80x2,5xe2x80x2-monophosphate (cAMP) phosphodiesterases were determined by measurement of their IC50 values (the concentration of compound required for 50% inhibition of enzyme activity).
The required PDE enzymes were isolated from a variety of sources, including human corpus cavernosum, human and rabbit platelets, human cardiac ventricle, human skeletal muscle and bovine retina, essentially by the method of W. J. Thompson and M. M. Appleman (Biochem., 1971, 10, 311). In particular, the cGMP-specific PDE (PDE5) and the cGMP-inhibited cAMP PDE (PDE3) were obtained from human corpus cavernosum tissue, human platelets or rabbit platelets; the cGMP-stimulated PDE (PDE2) was obtained from human corpus cavernosum; the calcium/calmodulin (Ca/CAM)-dependent PDE (PDE1) from human cardiac ventricle; the cAMP-specific PDE (PDE4) from human skeletal muscle; and the photoreceptor PDE (PDE6) from bovine retina. Phosphodiesterases 7-11 were generated from full length human recombinant clones transfected into SF9 cells.
Assays were performed either using a modification of the xe2x80x9cbatchxe2x80x9d method of W. J. Thompson et al. (Biochem., 1979, 18, 5228) or using a scintillation proximity assay for the direct detection of AMP/GMP using a modification of the protocol described by Amersham plc under product code TRKQ7090/7100. In summary, the effect of PDE inhibitors was investigated by assaying a fixed amount of enzyme in the presence of varying inhibitor concentrations and low substrate, (cGMP or cAMP in a 3:1 ratio unlabelled to [3H]-labeled at a conc xcx9c⅓ Km) such that IC50≅Ki. The final assay volume was made up to 100 xcexcl with assay buffer [20 mM Tris-HCl pH 7.4, 5 mM MgCl2, 1 mg/ml bovine serum albumin]. Reactions were initiated with enzyme, incubated for 30-60 min at 30xc2x0 C. to give  less than 30% substrate turnover and terminated with 50 xcexcl yttrium silicate SPA beads (containing 3 mM of the respective unlabelled cyclic nucleotide for PDEs 9 and 11). Plates were re-sealed and shaken for 20 min, after which the beads were allowed to settle for 30 min in the dark and then counted on a TopCount plate reader (Packard, Meriden, Conn.) Radioactivity units were converted to % activity of an uninhibited control (100%), plotted against inhibitor concentration and inhibitor IC50 values obtained using the xe2x80x98Fit Curvexe2x80x99 Microsoft Excel extension. Results from these tests show that the compounds of the present invention are potent and selective inhibitors of cGMP-specific PDE5.
This was assessed in vitro by determining the capacity of a compound of the invention to enhance sodium nitroprusside-induced relaxation of pre-contracted rabbit corpus cavernosum tissue strips, as described by S. A. Ballard et al. (Brit. J. Pharmacol., 1996, 118 (suppl.), abstract 153P).
Compounds were screened in anaesthetised dogs to determine their capacity, after i.v. administration, to enhance the pressure rises in the corpora cavernosa of the penis induced by intracavernosal injection of sodium nitroprusside, using a method based on that described by Trigo-Rocha et al. (Neurourol. and Urodyn., 1994, 13, 71).
Compounds of the invention may be tested at varying i.v and p.o. doses in animals such as mouse and dog, observing for any untoward effects.